Method of controlling chemical reactions



Patented Dec. 8., 1925.

UNITEDSTATES PATENT OFFICE.

' HERBERT H. DOW, OF MIDLAND, MICHIGAN, ASSIGHOB TO THE GHEKICAI:

COMPANY.

METHOD 01: C(lN'IROLLING CHEMICAL REACTIONS.

1T0 Drawing.

To all whom, it may concern.-

Be it known that I, HERBERT H. Dow, a citizen of the United States, and a resldent of Midland, county of Midland, and State of Michigan, have invented a new and .useful Improvement in Methods of Controlling Chemical Reactions, of which the following is a specification the principle of the invention being herein} explained and the best mode in which I have contemplated applying that principle, so as to istinguis it from other inventions. v

The present invention relating as indicated to methods of controlling chemical reactions, has more particular regard to the control of reactions in so-called fusion rocesses, and especially to the control 0 the temperatures of such reactions. While, within the range indicated, the invention has more or less general adaptability, I have discovered in applying the same. to the manufacture of indoxyl according to the original process of Heumann and subsequent im-- provements of such process, that new and unexpected results are secured of. very considerable importance in the commercial production of synthetic indigo. The invention will accordingly be described by a specific reference to a method of making indoxyl and derivatives wherein a phenyl-glycine' body is intermixed with a caustic alkali melt, the new results accomplished including, in addition to the control of the temperature of the melt in such fashion as to prevent any undue decomposition of the phenyl-glycine or equivalent body, the blanketing of the melt and of the un-reacted phenyl-glycine body against oxidation. At the same time I am' able to maintain such body in more completely disseminated condition in the fusion mixture, thus insuring a a uniformly satisfactory product.

' With regard to the provision of a blanket ing medium for the melt, which is an inci- 1 I mercial use of such modifiedprocesses has dental feature in the present case, I should remark that I have heretofore described and and the present improved method or process is designed among other things to achieve I this same result, but in a different manner.

ous modifications of such Application filed. December 8,1920. Serial No. 499,081.

- To the accomplishment of the foregoing and related ends, theinvention then consists of the ste s hereinafter fully described and particularg pointed out in the claims, the following escription setting forth in detail one approved mode of carrying out the invention, such disclosed mode, however, constitutin which t used.

As previously indicated, the making of in-. doxyl and its derivatives will conveniently serve by way of illustration of my improved method or pIrocess of controlling chemical reactions. the manufacture of synthetic indigo by the e principle of tlfi invention may be eumanns original process forv but one of the variousv ways infusion of phenyl-glyclne with caustic potash did not prove commercially practicable because of the small yield obtained and numerrocess have since been proposed, some by eumann himself (see U. S. Patent No. 617,652) for increasing the yield. Various theories moreover have been set forth in explanation of this unsatisfactory result, Friedlander for example suggesting (Fortschritte der Theerfarben-Industrie Part. II, p. 100) poor yield is due to the fact that the caustic alkalies destroy the indoxyl formed and break up the glycine before it undergoes transformation into indoxyl. In accordance with this theory dehydrating agents have been added to t e caustic potash or caustic soda or mixture of the two constituing the bulk of the fusion mixture, to assist the reaction and allow the temperature ofthe melt to be reduced below that which had to be 'employed when caustic alkalie's alone were used. Despite the fact that by such means a yield of indoxyl as high as 50 per cent of the weight of glycine has been achieved, the latter is so readily decomposed at the temperature at which it is introduced into the.

melt that a serious loss is entailed and comto a temperature ofapproximately 250 if the melt is to remain sufficiently fluid.

that such they are ordinarily use require to be raised There is thus only a very narrow range permitted and when it is further recalled that the increase in temperature during the heat of reaction due to the exothermic character of the latter may equal or exceed this range, the difliculties encountered in controlling the reaction will be obvious I have discovered that by mixing with the phenyl-glycine body before it is added to the fused caustics a neutral hydrocarbon oil such for example as commercial kerosene which contains constituents that boil at a temperature between that at which such caustics are molten and that at which such decompositionof the phenyl-glycine body sets in, the cooling effect of the evaporation of such oil will offset the heat of reaction and an approximately constant temperature can thus be maintained in the melt. The importance of this has already been sufiiciently empha-- sized, but an additional advantage follows in that by preventing an increase in temperpercent, the proportion of caustic soda beingature due to the reaction it is possible to operate with a much smaller percentage of caustic potash than has heretofore been the case, such caustic potash being the more exum hydroxide are specified, it has been found feasible by the present improved method to reduce the caustic potash to less than ten corres ondingly increased. To such mixture of caustic potash and soda I preferably add, as described in said Reissue Letters Patent, quicklime and metallic sodium in approximately the proportions set forth in the specific example in said patent and the amount of phenyl-glycine potassium (or sodium) salt employed is likewise inthe same proportion; in fact. the procedure will follow exactly that of the patent'in question exce t for the fact-that the henyl-glycine salt efore it is added to the sion' mixture consisting of such caustic potash, caustic soda, quicklime' and sodium, is thoroughly wetted with kerosene or equivalent neutral hydrocarbon oil. The amount of such oil employed will depend upon the size of the batch and other operative conditions; where, as in commercial practice, a melt weighing altogether a proximately 3000 oun'ds or more is mace up, the phenyl-g ycine saltmay be Wetted with kerosene until it will flow more or less freely, approximately equal amounts by weight of the phenyl-glycine salt and kerosene being found satisfactory.

In addition to keeping down the temperature of the fused mass to a point below that at which decomposition of the'phenyl-glycine body occurs at least in harmful degree, the neutral hydrocarbon oil protects such body against oxidation and upon volatilizing will find its way to the surface and there form a blanketing medium for the'melt exactly in tlie same-way as though such oil were simply dropped onto the surface as proposed in the fusion process described in my co-pending application above referred to. Such blanketmg vapor protectsthe fusion mixture and articularly any phenyl-glycine that may be oating on its surface from oxidation if the atmosphere above the fusion should ha v pen to contain a small amount of oxygen. foreover the phenyl-glycine thus wetted' with oil mixes much more readily with the caustic bath so that considerably.

less a itation is necessary than where dry pheny glycine is used. The wetted mate rial comes into better contact with the molten caustic and the vaporization of the oil tends to disintegrate any lumps or agglomerated masses of the material.

Even in the case of the specific reaction involved in the manufacture of indoxyl, different oils will be found to fulfill satisfactorily the requirements, in addition to kerosene which has been specifically mentioned. Thus, other mineral oils, i. e. petroleum distillates, of the same series, and various coaltar distillates, particularly those members of the benzene series which are neutral in character towards the phenyl-glycine body and caustic ingredients and which volatilize at the proper temperature, may be employed. The referred range of temperature at which the fusion should be held during the reaction is 230 and 285 centigrade, and the amount of any particular oil employed may be readily determined from a knowledge of its boiling point and latent heat of vaporization taken'in conjunction with the amounts of the other ingredients of the melt.

For that matter, since heat of course is absorbed inthe change of a body from solid to li uid form just as well as in changing rom a liquid to a gaseous form, substances that are solid at normal temperatures may, if otherwise suited, be employed to secure the control of temperature of the melt to a certain extent, as well as the desired dissemination of the material being reacted upon in such melt. Thus, for example, parafline can be used in the specific case cited although not as satisfactorily as kerosene, especially since the latter upon being volatilized rises to the surface ofthe melt and forms a blanketing medium over the same. So, too, by introducing the proper amount of solid, i. e. unmelted caustic, along with the phenyl-glycine body, the condition of the melt can be controlled in an analogous manner, the heat of the reaction being absorbed by the conversion of such additional caustic from such solid to molten condition.

It will be understood that the term phenylglycine body connotes not merely the specific phenyl-glyci-ne salt hereinbefore mentioned, but other derivatives and homologuesof phenyl-glycine, including the esters and anliydrides of henyl-glycine and its homologues, phen -glycine and its homologues, and like bo ies. Moreover, it will be evident that the underlying principle of controlling chemical reactions by the inclusion in the reaction zone of a neutral substance adapted to change its physical form, with attendant absorption by heat at a temperature below that at which either an ingredient or the product is decomposed, is of general applicability and not limited to socalled fusion processes.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

I therefore particularly point out and distinctly claim as my invention 1. In a method of making indoxyl audits derivatives, the steps which consist in intermixing a phenyl-glycine body with a caustic alkali melt, and including in the mixture :1 neutral hydrocarbon oil adapted to be vaporized at a temperature between that at which such caustic alkali is molten and that at which decomposition of such phenyl-glycine body sets in.

2. In a method of making indoxyl and its derivatives, the steps which consist in intermixing a henyl-glycine body with a caustic alkali melt, and including in the mixture a neutral mineral oil having a boiling point alkali melt, andincluding erosene in the mixture. I

4. In a method of making indoxyl and its derivatives, the ste s which consist in wettin a phenyl-glycine body with a neutral hydrocarbon oil, and then intermixing the same with a caustic alkali melt.

5. In a method of makin indoxyl and its derivatives, the steps which consist in wetting a phenyl-glycine body with a mineral oil having a boiling point below that at which decomposition of such phenyl-glycine body sets in; and then intermixing the same with a caustic alkali melt.

6. In a method of making indoxyl and its derivatives, the steps which consist in wetting a phenyl-glycine body with kerosene; and then intermixingthe same with acaust-ic' alkali melt.

Signed by me this 4th day of December, 1920.

HERBERT H. DQW. 

